Telecentric lens assembly providing a collimated light space

ABSTRACT

Systems and methods for imaging a target are provided. A system includes a detector and a substantially bitelecentric lens assembly positioned between the detector and the target. A first optical assembly is configured to focus light received from the substantially bitelecentric lens assembly onto the detector. The substantially bitelecentric lens assembly and the first optical assembly are configured to produce a collimated light space between the substantially bitelecentric lens assembly and the first optical assembly. A second optical assembly is positioned within the collimated light space.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/173,290, filed on Feb. 5, 2014, which is now U.S. Pat. No. 9,513,470,issued Dec. 6, 2016, which claims priority to U.S. Provisional PatentApplication No. 62/760,976, filed Feb. 5, 2013. The content of both arehereby incorporated by reference herein.

TECHNICAL FIELD

This invention relates to imaging systems, and more particularly, to useof a telecentric lens assembly providing a collimated light space.

BACKGROUND

A telecentric lens is a compound lens which has its entrance or exitpupil at infinity. In other words, the chief rays, that is, oblique rayswhich pass through the center of the aperture stop, are parallel to theoptical axis in front of or behind the system, respectively. An entrancepupil at infinity makes the lens object-space telecentric. Such lensesare used in machine vision systems because image magnification isindependent of the object's distance or position in the field of view,referred to as an orthographic view. An exit pupil at infinity makes thelens image-space telecentric.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, an imaging systemincludes a detector and a substantially bitelecentric lens assemblypositioned between the detector and the target. A first optical assemblyis configured to focus light received from the substantiallybitelecentric lens assembly onto the detector. The substantiallybitelecentric lens assembly and the first optical assembly areconfigured to produce a collimated light space between the substantiallybitelecentric lens assembly and the first optical assembly. A secondoptical assembly is positioned within the collimated light space.

In accordance with another aspect of the present invention, a method isprovided for imaging a target in accordance with an aspect of thepresent invention. A target is aligned in a field of view of anobject-side telecentric lens assembly having a first auxiliary opticalelement in a collimated light space. The target is imaged using thefirst optical element with an imaging system associated with thetelecentric lens. A second auxiliary optical element is exchanged forthe first auxiliary optical element without disturbing the alignment ofthe target at the telecentric lens. The target is then imaged using thesecond auxiliary optical element with the image system.

In accordance with yet another aspect of the present invention, akinetic imaging plate reader system is provided. The system includes adetector and a lens assembly positioned between the detector and amicroplate. An optical assembly is configured to focus light receivedfrom the lens assembly onto the detector. The lens assembly and thefirst optical assembly are configured to produce a collimated lightspace between the lens assembly and the first optical assembly. A firstfilter is positioned within the collimated light space. The first filteris configured to be modular, such that the first filter can be removedand replaced with a second filter without substantial disturbance of anyof the detector, the lens assembly, and the optical assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system for imaging a target in accordance with anaspect of the present invention;

FIG. 2 illustrates one implementation of a system for imaging a targetin accordance with an aspect of the present invention; and

FIG. 3 illustrates a method for imaging a target in accordance with anaspect of the present invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a system 10 for imaging a target 12 in accordancewith an aspect of the present invention. The system 10 includes adetector 14 and a substantially bitelecentric lens assembly 16positioned between the detector 14 and the target 12. The substantiallybitelecentric lens assembly 16 is configured to have an entrance pupilat an infinite distance from the lens, and an exit pupil that is asignificant distance from the lens, such that the chief rays of lightemitted from the lens assembly 16 are substantially parallel to anoptical axis of the system. By “substantially parallel,” it is meantthat the chief rays form an angle no greater than fifteen degrees withthe optical axis. By “substantially bitelecentric,” it is meant that thechief rays of light entering and emitted from the lens are substantiallyparallel to the optical axis of the system.

A first optical assembly 18 is positioned between the substantiallybitelecentric lens assembly 16 and the target 14. The first opticalassembly 18 is configured to focus light from the substantiallybitelecentric lens assembly 16 onto the detector 14, such that an imageplane of the substantially bitelecentric lens assembly falls between thelens assembly and the first optical assembly 18. It will be appreciatedthat, in accordance with an aspect of the present invention, the chiefrays of light emitted from the lens assembly 16 are substantiallyparallel for at least a portion of the region between the bitelecentriclens assembly and the first optical assembly 18. In one implementation,the first optical assembly 18 can be a substantially object-spacetelecentric lens assembly configured to receive the substantiallyparallel light rays from the substantially bitelecentric lens assembly16 onto the detector 14. By “substantially object-space telecentric,” itis meant that the chief rays of light entering the optical assembly aresubstantially parallel to the optical axis of the system.

To this end, a second optical assembly 20 can be positioned between thesubstantially bitelecentric lens assembly 16 and the first opticalassembly 18, such that the second optical assembly 20 is within theregion for which the chief rays of light emitted from the substantiallybitelecentric lens assembly 16 are substantially parallel, a collimatedlight space. In one implementation, the second optical assembly 20 caninclude one of a filter, a dichroic mirror, and a beam splitter. In oneimplementation, the second optical assembly 20 can be one of a set ofstandard, off-the-shelf emission filters configured in a high-speedrotary filter wheel to allow for rapid switching of filters into thecollimated light space. These filters can include, for example, any ofspectral filters, such as longpass filters, shortpass filters, neutraldensity filters, polarizers, and dichroic filters. In oneimplementation, the collimated light space could also accommodate amicro-filter array (MFA) for multispectral or hyperspectral imaging.This could be a pixel-matched MFA that is fixed within the collimatedspace or a coarser array, for example, with elements corresponding tothree-pixel by three-pixel blocks to the aperture of a microlens arrayand translated rapidly within a plane parallel to the optical axis withan actuator, such as a piezoelectric actuator. In anotherimplementation, the second optical assembly 20 can be a microlens array,a micropolarizer array, a micro-prism array, and a micro-diffractiongrating array

In one implementation, the system 10 is part of a kinetic imaging platereader system, and the target 12 is a microplate. In thisimplementation, the collimated light space can be used, for example, toenable rapid switching of commercially available filters withrestrictive design specifications. Such a system could further includean automated liquid handling system configured to dispense liquid into aplurality of wells in the microplate. Accordingly, the microplate couldpositioned above each of the detector 14, the substantiallybitelecentric lens assembly 16, and the first optical assembly 18 suchthat the microplate is freely accessible to the automated liquidhandling system. It will further be appreciated that the imaging systemcould be configured for use with any of visible light, infrared light,ultraviolet light, and microwave radiation as well. For example, whilethe plate reader might be configured to detect visible light, in oneimplementation, the target 12 might be an integrated circuit, and thesystem might be part of an integrated circuit testing assembly. In sucha case, the lens assembly 16 might be configured to image within theinfrared band. A non-exhaustive list of other applications can includenext generation sequencing applications, protein and nucleic acidmicroarray analysis, electrophorectic gel and blot analysis, and wholeanimal imaging.

FIG. 2 illustrates an imaging system 100 incorporating a lensarrangement 102 designed specifically to have a high light gatheringability and to produce an essentially distortion-free image of a target112. In the illustrated implementation, the target 112 can have a heightof about one hundred thirty-six millimeters, and the lens arrangement102 can be positioned about 67.6 millimeters from the target, and havean overall length, along its optical axis, of approximately 330.2millimeters. A detector 114 is configured to collect light from the lensarrangement 102. In the illustrated implementation, the detector has adiagonal dimension of around 18.8 millimeters.

In accordance with an aspect of the present invention, there is acollimated light space 119 in the lens arrangement 102 where the lightrays have been made substantially parallel with the long axis of thelens allowing optical elements 120 to be placed within the lens in a waythat preserves their ability to perform within their designspecifications. For example, elements such as filters and dichroicmirrors can require that light incident on the element have a specificangle of incidence and using these filters or mirrors outside of thelimits of their design specifications can significantly degrade theperformance of the element. Accordingly, the element 120 can includerelatively small, low mass, commercially available filters to beincorporated into a high-sensitivity, distortion-free optical trainproducing very flexible, versatile, and very high-performing imagingsystem 100 that is superior to what is presently used in plate-basedimagers.

The lens arrangement 102 includes a substantially bitelecentric lensassembly 116 configured to collect light from the target 112 and providethe light aligned appropriately for the collimated light space 119associated with the optical element 120. In the illustratedimplementation, the substantially bitelecentric lens assembly 116includes two doublet lens sets 122 and 124. A first doublet lens set 122includes a plano-convex lens, with the planar side oriented toward themicroplate target 112, and a positive meniscus lens, with the concaveside oriented toward the second doublet lens set 124. The second doubletlens set 124 includes a negative meniscus lens, with the convex sideoriented toward the first doublet lens assembly 122, and a biconcavelens. The light rays leaving the second doublet lens assembly 124 aresubstantially parallel with an optical axis of the lens arrangement 102.

The lens arrangement 102 further includes a substantially object-spacetelecentric lens assembly 118, separated from the substantiallybitelecentric lens assembly 116 by the collimated light space 119. Inthe illustrated implementation, the distance between the substantiallybitelecentric lens assembly 116 and the substantially object-spacetelecentric lens assembly 118, and thus the length of the collimatedlight space 119, is around 37.8 millimeters. A height of the collimatedlight space 119, and thus an approximate height of the lens assemblies116 and 118 at the point closest to the collimated light space 119, isaround forty-six millimeters. The substantially object-space telecentriclens assembly 118 focuses light from the collimated light space onto thedetector 114. Taken as a whole, the lens arrangement 102 provides alarge format, high light-gathering (e.g., a focal ratio on the order ofF/1.78) object-side telecentric lens with a filter-friendly collimatedspace 119 for filters and other optical components with limited designspecifications.

In accordance with an aspect of the present invention, the opticalelement 120 can be part of a set of multiple excitation and emissionfilters selected to support a broad ranging of fluorescent probes aswell as fluorescence polarization, fluorescence resonance energytransfer (FRET), and bioluminescence resonance energy transfer (BRET)that can be readily swapped into the collimated light space 119. Forexample, the filters can include a filter set appropriate for bluefluorescent protein (BFP), a filter set appropriate for red fluorescentprotein (RFP), and a filter set appropriate for green calcium orthallium-sensitive fluorescent dye.

It will be appreciated that the object-side telecentric lens arrangement102 of the current invention provides a number of advantages, includinga constant level of magnification, low distortion, and cancellation ofperspective effects. In addition, the collimated light space 119 allowsfor rapidly changing of filters and other optical components fordifferent kinds of contrast, polarization, and off-axis lightintroduction. All of these properties are useful for applications suchas machine vision, metrology, and astronomy.

The ability to change filters can also be useful for multicolor imagingin gene sequencing, as well as multicolor imaging with whole animals orlarge pathology sections. In addition, the lens arrangement 102 has veryhigh light-gathering (e.g., a focal ratio on the order F/1.8 as opposedto F/12-16 for existing telecentric lens designed for industrial machinevision applications), and a relatively narrow depth of field. High lightgathering is important for low-light imaging in microplates, and thenarrow depth of field is important for some amount of out-of-focus lightrejection. In microplate imaging, the target may be a thin cell layer onthe bottom of a plate covered by fluorescent fluid, making thisout-of-focus rejection useful for avoiding spurious results. Finally,the combination of telecentricity, low light gathering, and filterchanging is useful for gel imaging systems where multiple fluorescentantibodies are used to label proteins electrophoretically separated on agel.

In view of the foregoing structural and functional features describedabove, a methodology in accordance with various aspects of the presentinvention will be better appreciated with reference to FIG. 3. While,for purposes of simplicity of explanation, the methodology of FIG. 3 areshown and described as executing serially, it is to be understood andappreciated that the present invention is not limited by the illustratedorder, as some aspects could, in accordance with the present invention,occur in different orders and/or concurrently with other aspects fromthat shown and described herein. Moreover, not all illustrated featuresmay be required to implement a methodology in accordance with an aspectof the present invention.

FIG. 3 illustrates a method 100 for imaging a target in accordance withan aspect of the present invention. At 102, a target is aligned in afield of view of an object-side telecentric lens assembly having a firstauxiliary optical element in a collimated light space. By a “collimatedlight space,” it is meant a region of the optical train of the lensassembly in which the chief light rays are substantially parallel. Inone implementation, the object-side telecentric lens assembly has afocal ratio less than F/2. At 104, the target is imaged using the firstoptical element with an imaging system associated with the telecentriclens. At 106, a second auxiliary optical element is exchanged for thefirst auxiliary optical element without disturbing the alignment of thetarget at the telecentric lens. At 108, the target is imaged using thesecond auxiliary optical element with the image system.

Many optical elements, such as filters, beam splitters, and dichroicmirrors, have relatively tight design tolerances, and will not functionproperly if the angle of incidence of incoming light is too great.Accordingly, it is often necessary to utilized specialized elements atfixed locations within the optical train to provide these functions.Because the collimated light space is compatible with the designspecification of these components, they can be exchanged freely, withoutdisturbing the lens assembly or the alignment of the lens assembly withthe target. In one implementation, the optical assemblies can bemicrofilter arrays. In another implementation, the first and secondauxiliary optical elements are filters on a high-speed rotary filterwheel. In this case, the optical elements can be exchanged withoutdisturbing the alignment by rotating the high-speed rotary filter wheel.

What have been described above are examples of the present invention. Itis, of course, not possible to describe every conceivable combination ofcomponents or methodologies for purposes of describing the presentinvention, but one of ordinary skill in the art will recognize that manyfurther combinations and permutations of the present invention arepossible. Accordingly, the present invention is intended to embrace allsuch alterations, modifications, and variations that fall within thescope of the appended claims.

What is claimed is:
 1. An imaging system comprising: a detector; a lensassembly, positioned between the detector and a target; a first opticalassembly configured to focus light received from the lens assembly ontothe detector, the lens assembly and the first optical assembly beingconfigured to produce a collimated light space between the lens assemblyand the first optical assembly; and a beam splitter positioned withinthe collimated light space.
 2. The imaging system of claim 1, whereinthe lens assembly is substantially image-space telecentric.
 3. Theimaging system of claim 1, wherein the beam splitter comprises apolychroic mirror.
 4. The imaging system of claim 3, wherein thepolychroic mirror comprises a bichroic mirror.
 5. The imaging system ofclaim 4, wherein the second optical assembly is at least one of amicrofilter array, a microlens array, a micropolarizer array, amicro-prism array, and a micro-diffraction grating array.
 6. The imagingsystem of claim 4, wherein the second optical assembly is one of alongpass filter, a shortpass filter, a neutral density filter, apolarizer, and a dichroic filter.
 7. The imaging system of claim 1,further comprising a second optical assembly positioned within thecollimated light space.
 8. The imaging system of claim 7, wherein thesecond optical assembly is configured to be modular, such that thesecond optical assembly can be removed and replaced with a third opticalassembly without disturbance of the detector, the lens assembly, and thefirst optical assembly.
 9. The imaging system of claim 8, wherein eachof the second optical assembly and the third optical assembly compriseat least one filter configured in a filter changer.
 10. The imagingsystem of claim 1, wherein the target is an integrated circuit and theimaging system is part of an integrated circuit testing system.
 11. Theimaging system of claim 1, wherein the target is a microplate, and theimaging system is part of a plate reader.
 12. The imaging system ofclaim 1, wherein a lens arrangement comprising the first lens assemblyand the first optical assembly has a focal ratio less than F/2.
 13. Theimaging system of claim 1, wherein the at least one of the dichroicmirror and a beam splitter is configured to be modular, such that the atleast one of the dichroic mirror and a beam splitter can be removed andreplaced with another beam splitter or dichroic mirror withoutdisturbance of the detector, the lens assembly, and the first opticalassembly.
 14. A method for imaging a target comprising: aligning atarget in a field of view of lens assembly having a filter in acollimated light space; imaging the target using the filter with animaging system associated with the lens assembly; exchanging a secondfilter for the first filter without disturbing the alignment of thetarget at the lens assembly; and imaging the target using the secondfilter with the image system.
 15. The method of claim 14, wherein thefirst and second filters are deployed on a filter changer, andexchanging the second filter for the first filter without disturbing thealignment of the target at the lens assembly comprises activating thefilter changer.
 16. The method of claim 14, wherein the lens assemblyhas a focal ratio less than F/2.
 17. A plate reader system comprising: adetector; a lens assembly, positioned between the detector and amicroplate; an optical assembly configured to focus light received fromthe lens assembly onto the detector, the lens assembly and the firstoptical assembly being configured to produce a collimated light spacebetween the lens assembly and the first optical assembly; at least oneof a dichroic mirror and a beam splitter positioned within thecollimated light space; and a first filter positioned within thecollimated light space, the first filter being configured to be modular,such that the first filter can be removed and replaced with a secondfilter without substantial disturbance of any of the detector, the lensassembly, and the optical assembly.
 18. The plate reader system of claim17, further comprising an automated liquid handling system configured todispense liquid into a plurality of wells in the microplate.
 19. Theplate reader system of claim 18, wherein the microplate is positionedabove each of the detector, the lens assembly, and the optical assemblysuch that the microplate is freely accessible to the automated liquidhandling system.
 20. The plate reader system of claim 17, wherein thefirst and second filters are part of a set of excitation and emissionfilters selected to support fluorescent probes, the set of filtersincluding at least one filter configured to selectively passing lightfrom blue fluorescent protein, at least one filter configured toselectively passing light from red fluorescent protein, and at least onefilter configured to selectively passing light from one of green calciumand thallium-sensitive fluorescent dye.